After some searching and digging, I found the cause. I had followed Andrew Escobar’s excellent guide to getting Front Row to work on my (unsupported) PowerBook G4. The update to 10.4.5 patched some of the file used to make the Front Row hack work, so they started crashing. The solution is rather simple. This assumes you already had Front Row installed and working, and now it is erroring out. If you want to install it for the first time, I recommend you read Andrew’s Directions.